Laboratory heater



Feb. 12, 1929. 1,702,078

H. GOLDBERG LABORATORY HEATER Filed Aug. 8, 1925 vrwkj,

Patented Feb. 12, 1929.

UNITED STATES PATENT OFFICE.

HERMAN G-OLDBERG, OF CHICAGO, ILLINOIS, ASSIGNOR TO PRECISION SCIENTIFIC CO., OF CHICAGO, ILLINOIS, A CORIORATION OF ILLINOIS.

LABORATORY HEATER.

Application led August 8, 1925.

This invention relates to improvements in laboratory heaters and its purpose is to proan improved device adapted particularl y for use in chemical laboratories and the like tor applying heat to the various vessels and appliances which are employed in chemical operations and experiments. The principal object J the invention is to provide an improved eiectrical heater tor laboratory use. Another object is to provide a simplified form of heater comprising a minimum number olil parte. which may be constructed at small cost and conveniently assembled. A further obect is to provide an improved electrically operated heater comprising improved means for controlling the degree of heat. Other objects relate to various features of construction and arrangement which will appear more fully hereinafter.

T he nature of the invention will be understooi. rom the 'following specification taken with the accompanying drawings in which,

In Fig i 2, 3 and l or" the drawings, there is l one inodiication of the invention compi i ng means tor regulating the neat produced by the electrical heating elements. In this torni, there is provided a rectangular housing 60 of sheet-metal or the like provided at its corners with relatively short legs 6l adapted to rest upon a suitable support and provided also in its lateral walls with holes 12 for the purpose oi' furnishing ventilation in that portion ot the device beneath the heating element. In forming the ve ilating apertures (52, a number of inwardly en-tcnding ears are formed and these are adapten to support a heat insulating plate whch rests rectly thereon and which prevents the downward passage of heat )reduced by 'the heating plate mounted thereon. The heating plate 65 comprises a te ot baked clay5 porcelain or the like hav- A.g a plurality of grooves 66 which are con- '..ected their alternate ends to form a zigzag recess Gi' in which there is mounted the fli Serial No. 48,970.

heating elementl 68 having its ends connected to the terminals 69 which are secured to the underside of the plate 65. The terminals 69 of the electrical heating element are connected to conductors leading from a suitable source of electrical energy and the heat produced by the electrical heating element 68 is transferred upwardly to the top plate 70 which may have any desired form, being illustrated in Fig. 2 as a rectangular plate having an annular rib TEL around its outer edge and provided centrally with a circular opening 70h around which there is an inclined wall 7()c for engagen'ient with the loWer end of a iiask or other vessel employed in chemical work or the like. This top plate 70 extends downwardly within the housing (SO and rests directly on the top surface oi' the heating plate 65.

In the form of the invention illustrated in Figs. l, 2, 3 and 4, the terminals 69 of the heating element are connected to a device for regulating the heat. For this purpose, one terminal 69 isconnected by a conductor 72 to one terminal ot the source of electrical energy and the conductor 'leading trom the other terminal of that source is connected to one end of a conductor 75 which serves as a resistance to regulate the heat produced. The resistance wire 75 is wound in two helical coils 76 which are located on insulating tubes 77 extending between the opposite walls .of the housing 60 and the end or' the resistance wire 75 opposite the supply conductor 723 is connecte-d to the other terminal 69 of the heating element 68. The connections of the resistance wire 75 to the conductor 73 and to the heating element 68 are made at the same ends otx the supporting tubes 77 and the length oi the resistance wire T which is included in the circuit is determined by the position oit a short-circuiting contact plate 78 carried by a block .79 which is slidably mount-- ed on a rod 80 extending between the side walls of the housing 60 to which it is secured. The contact plate 78 has downwardly turned extremities 78a which are adapted to Contact with the peripheral surfaces of the helical coils 76 and the contact plate is secured at its central part to an inverted cup-shaped member 8l which is mounted for vertical movement in agniding member 82 formed of insulating material and embedded in the block 79. A coil spring 83 is mounted within the cupshaped member 8l and engages the lower Wall of the member 82, thus maintaining` the Contact plate 78 in close contact with the coils 76 of the resistance element 75. The rod 80 has rack teeth 84'tor1ned on its under side to mesh with a pinion 85 which is fixed on a shaft 86 ournaled in the blocl 79 and extending,` outwardly through a slot 88 formed in the front wall of the housing,- 60. 'The outer end of the shaft 86 is provided with a handle 89 and an indicating plate'Q() is secured to the housing 60 above the slot 88 for the purpose of indicating' the temperature produced with the Contact )late 7 8 in Adifferentpositions. lt

Will be apparent that upon rotation of the shaft 86, the bloclr 79 is adjusted longitudinally by the engagementot the pinion 85 with the rack teeth 84, thus regulating the portion of the resistance coils which are in the circuit and thereby producing diterentiteinperatures in the heating' element 68. rllhe different positions ot the block 7 9 and the contact plate 7 8 and the temperatures corresponding' thereto are indicated by graduations 91 on the plato 90 and this plate also carries anV indicating arrow 92 which indi cates the direction oi"- movement for increasing; the temperature. By this simple vdevice which is embodied in the heating' device aV part of the permanent assembly, it is possible 'handle 89 may be adjusted to position the shaft 86 beneath the same graduation 91 on the indicating plate 90.

Although a certain form of the invention has been shown and described by Way or illustration, it will be understood that the inven tion may be embodied in various other forms Within the scope of the appended claim.

l claim:

A heatin@ device comprisingl a sheet metal casing havin g a plurality of Ventilating openings punched in the wall thereof and forming a plurality ot inwardly projecting tongues, a heatl insti-dating` partition resting on said tongues, a heating plate resting` on the top surl'ace of said partition, a heating element carried by said heating plate, a top plate resting; on said heating plate having means for supporting a vessel, an electric circuit for said heating element, a rheostat located in the "otter part of said casing` and beneath said rrtition and connected in said circuit, and neans. operable from the outside of said casing for regulating` said rheostat.v

HERMAN GOLDBERG, 

